During the past ten years, various different kinds of breadmaking machines have been introduced into the consumer market. All of these bread-making machines automatically mix and knead dough once the necessary ingredients have been provided, let the dough rise and then bake the dough into a loaf of bread of a desired crispness. Electronic circuitry is integrated within the apparatus and can be programmed to execute the different steps in their certain desired order and timing depending on the kind of bread a user desires to bake. In this way, all the user has to do is to place the correct specified ingredients into the baking pan and to select the bread type corresponding to the ingredients.
Existing prior art bread-making machines essentially include, a baking pan, a kneading blade provided in the bottom portion of the baking pan and an electric motor which rotates the kneading blade for a predetermined period of time. The pan, which has an open top, is removable from the appliance in order to extract the ready loaf from the pan as well as for cleaning purposes. The pan is surrounded by a baking chamber, the baking chamber being provided with an open top portion which is tightly closed by a cover during bread making. The baking chamber contains a heating element in its bottom portion which can be energized to the correct temperature and timing by the aforementioned electronic circuitry. The air heated in the baking chamber transmits the heat energy to the dough in the baking pan by natural convection through the open top portion and by conduction through the metallic walls. An outer housing encloses the baking chamber and contains, inter alia, the electric motor and drive for rotating the kneading blade, the electronic circuitry and a keyboard for selecting the suitable bread type.
Existing bread making machines have certain drawbacks. Some these drawbacks include the fluctuations and uneven distribution of temperature in the baking chamber, with higher temperature air rising to the top and lower temperature air remaining near the bottom. As a result of this temperature differential, a prior art temperature sensor will not be able to deenergize the heater whenever the correct baking temperature has been reached, thus causing large temperature fluctuations during the baking process which result in the problems associated in baking of the bread ie. uneven and incomplete baking. A second drawback is that the outer housing becomes excessively hot by the convection and radiation from the hot wall of the baking chamber during the long baking time. In view of this excessive heat, prior art machines require that the housing be made of metal instead of plastic material. As is obvious, a plastic housing is less costly and more aesthetically acceptable than a metal one. Additionally, in order to overcome the temperature fluctuations and the uneven temperature distributions described previously, most bread making apparatuses include a baking pan of heavy die-cast aluminum adding considerably to the total cost of the appliance.
It is the main object of the present invention to eliminate these drawbacks and to provide a bread-making apparatus wherein the air surrounding the baking pan remains at a substantially uniform temperature during the entire baking process.
It is another object of the present invention to increase the heat transfer to the dough in the baking pan by providing hot air flow along the metallic walls of the baking pan, thereby accelerating the baking process and shortening the baking time. By providing air flow around the metallic walls of the baking pan, it becomes possible to replace the previously mentioned heavy baking pan by a low-cost thin-walled pan altogether.
It is a further object of the invention to provide means for cooling the outside of the baking chamber and thereby prevent the outer casing from being heated to an unpleasantly high degree.
It is an additional object of the invention to provide the apparatus with an outer housing made of a plastic material which results in a substantial cost reduction without the danger of a user being burned by an excessively hot surface.
Additionally, applicants incorporate by reference the disclosure of U.S. application Ser. No. 08/503,652, filed concurrently herewith and also entitled "AUTOMATIC BEAD-BAKING MACHINE".
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.